Lower molecular weight alcohols and ethers such as isopropanol (IPA) and diisopropyl ether (DIPE) are in the gasoline boiling range and are known to have high blending octane numbers. In addition, by-product propylene from which IPA and DIPE can be made is usually available in a fuels refinery. One important focus of research in the petroleum industry is processes to produce high octane gasolines blended with lower aliphatic alkyl ethers as octane boosters and supplementary fuels. Generally, it is known that asymmetrical C.sub.5 -C.sub.7 alkyl tertiary alkyl ethers and diisopropyl ether (DIPE) are particularly useful as octane improvers for liquid fuels, especially gasoline. MTBE, ethyl tert-butyl ether (ETBE), isopropyl tert-butyl ether (IPTBE) and TAME are known to be high octane ethers. The article by J. D. Chase, et al., Oil and Gas Journal, Apr. 9, 1979, discusses the advantages one can achieve by using such materials to enhance gasoline octane. The octane blending number of MTBE when 10% is added to a base fuel (R+O=91) is about 120. For a fuel with a low motor rating (M+O=83) octane, the blending value of MTBE at the 10% level is about 103. On the other hand, for an (R+O) of 95 octane fuel, the blending value of 10% MTBE is about 114. Increasing demand for high octane gasolines blended with high octane ethers as octane boosters and supplementary fuels has created a significant demand for these ethers, especially MTBE and TAME. Improvements to the processes related to the production of these ethers are matters of high importance and substantial challenge to research workers in the petroleum refining arts.
The catalytic hydration of olefins to provide alcohols and ethers is a well-established art and is of significant commercial importance. Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 2,262,913; 3,798,097; 3,198,752; 3,810,848; 3,989,762, among others.
The production of ether from secondary alcohols such as isopropanol and light olefins is also known. As disclosed in U.S. Pat. No. 4,182,914, DIPE is produced from IPA and propylene in a series of operations employing a strongly acidic cation exchange resin as catalyst.
It is well known that isobutylene may be reacted with methanol over an acidic catalyst to provide methyl tertiary butyl ether (MTBE) and isoamylenes may be reacted with methanol over an acidic catalyst to produce tertiary amyl methyl ether (TAME). The reaction is a useful preparation for these valuable gasoline octane enhancers and is typical of the reaction of the addition of lower alkanol to the more reactive tertiary alkenes, or iso-olefins, of the type R.sub.2 C=CH.sub.2 under mild conditions to form the corresponding tertiary alkyl ethers. The feedstock for the etherification reaction may be taken from a variety of refinery process streams such as the unsaturated gas plant of a fluidized bed catalytic cracking operation containing mixed light olefins, preferably rich in isobutylene. Light olefins such as propylene and butenes other than isobutylene in the feedstock are essentially unreactive toward alcohols under the mild, acid catalyzed etherification reaction conditions employed to produce lower alkyl tertiary butyl ether.
The crude methanol source for methanol for the MTBE reaction typically contains a significant amount of water. For the etherification reaction to proceed effectively it is important that water in the crude methanol be reduced. In the DIPE process, the reaction of water with propylene to produce DIPE also produces a by-product stream consisting of isopropanol and water. To maintain high conversion it is required in the prior art that this stream be recycled to the DIPE unit.
It is an object of the present invention to provide an integrated process for the manufacture of alkyl tertiary alkyl ethers using dewatered alkanol byproduct from linear olefins hydration as feedstream to iso-olefins etherification.
Another object of the present invention is to provide a process for the manufacture of methyl or isopropyl tert-alkyl ether and diisopropyl ether in a design integrated with DIPE production.
It is another object of this invention to provide an integrated MTBE and DIPE process which additionally produces isopropyl tert-butyl ether.
Yet another object of the present invention is to provide an integrated process for the manufacture of high octane ethers containing methyl tert-alkyl ethers, DIPE and including high octane gasoline.